Simple Methods to Estimate Growth Traits in a High Yielding Rice Cultivar ‘Tsukiakari’ in Hokuriku Regions

Abstract

For the early maturity and high palatable rice cultivar, ‘Tsukiakari’, to attain the maximum grain yield of 750 g m^–2, it is important to achieve 35700 spikelets per square meter. We examined the relationship between growth parameters and amount of nitrogen application at the panicle neck node differentiation stage, to attain a high yield and high palatability. Based on a significant linear regression between growth traits, shoot nitrogen content and leaf color based on the single photon avalanche diode (SPAD) value at full heading stage were estimated to be 13.4 g m^–2 and 41.9, respectively, when 35700 spikelets per square meter was achieved. Growth parameters showed a close correlation at the panicle neck node differentiation stage, represented by a significant linear regression. The normalized difference vegetation index (NDVI) value was in the range of 0.26–0.75 and showed a positive and close correlation with growth index value (plant height cm × number of tillers per square meter × SPAD value), indicating that NDVI can be used to estimate the growth index value in ‘Tsukiakari’ at the panicle neck node differentiation stage. We also elucidated that the NDVI value was greatly affected by water depth in the paddy field, and developed a calculation model to estimate the growth parameters of ‘Tsukiakari’ at the panicle neck node differentiation stage by adjusting the NDVI value to the water depth.